FIG. 12 is a cross-sectional view illustrating a conventional electro-acoustic transducer that is used as a loudspeaker or a receiver included in an electronic apparatus such as a portable telephone unit. Magnet 1 is disposed between upper plate 2 and yoke 3 to provide an inner magnet-type magnetic circuit. Yoke 3 is press-fit into resin-made frame 6 and integrated by gluing. Diaphragm 7 is fixed to frame 6 at the circumferential edge. Voice coil 8, which is for vibrating diaphragm 7, is attached to diaphragm 7 and is placed in magnetic gap 5 of magnetic circuit 4.
Lead wire of voice coil 8 is soldered with one end of terminal 10. Frame 6 is provided with terminal 10, which is molded partially in the frame. Terminal 10 is bent-up at center section 10A so as not to protrude from the outer boundary of frame 6. Terminal 10 is formed by bending a conductive metal sheet and movable end 10B has a contact with an electric supply section of a system taking advantage of a spring force of metal sheet. Movable end 10B is bent to have a loop-like shape to provide stopper 10C.
FIG. 13 is a cross-sectional view illustrating another conventional electro-acoustic transducer. FIG. 13 has the same structure as that of FIG. 12 except for that stopper 10D protruding to frame 6 is provided in the vicinity of movable end 10B of terminal 10.
In both of the structures shown in FIG. 12 and FIG. 13, stoppers 10B and 10C are provided by machining the vicinity of movable end 10B of terminal 10. Stoppers 10B and 10C both restrict a bending range of terminal 10 so as to prevent a metal sheet constituting terminal 10 from being bent to a level exceeding a reversibility limit value of a metal material constituting terminal 10. This prevents, even when loudspeakers 11A and 11B are strongly pressed while being attached to an apparatus, terminal 10 from being bent to a level exceeding a reversibility limit value. This solves an inconvenience, for example, where terminal 10 is broken while loudspeakers 11A and 11B are attached to an apparatus or terminal 10 has an insufficient spring pressure to cause an unstable contact between terminal 10 and the apparatus. Loudspeakers 11A and 11B are disclosed, for example, in Japanese Patent Unexamined Publication No. 2003-37890.
However, when loudspeakers 11A and 11B have much dimensional margin for attaching loudspeakers 11A and 11B to an apparatus such as a portable telephone unit, stoppers 10C and 10D themselves may be deformed. Furthermore, when an apparatus including loudspeaker 11A or 11B is dropped due to a careless handling, stoppers 10C and 10D may be collapsed by an excessive impactive force. These are caused because, although stoppers 10C and 10D are both made of the same type of metallic terminal and thus have a spring pressure, stoppers 10C and 10D can be deformed permanently when stoppers 10C and 10D receive a force exceeding the reversibility limit value of the spring pressure. When stoppers 10C and 10D are deformed as described above, the reversibility limit value of the spring pressure of the metal terminal of terminal 10 is exceeded. This causes the contact with an electric supply section of the apparatus to be unstable. Thus, poor contact is caused and thus signal transfer is interrupted when the apparatus receives an impact or when the apparatus is vibrated.
The inconveniences as described above are caused not only in the type where terminal 10 includes stopper 10C or 10D but also in the type where frame 5 is integrated with a stopper by resin when frame 6 is subjected to injection molding. In this type, the terminal is exceeded in the reversibility limit value of the spring pressure of the metal terminal when the resin stopper is broken by an impact.